1. Field of the Invention
The present invention relates generally to a composite roofing product made up of a sheet of vulcanized rubber to one side of which is adhered a fleece matting via a polymeric film bonding agent and to the other side of which is adhered a layer of roof covering granules. An apparatus and method for cleaning vulcanized rubber and for making the composite roofing product is also disclosed.
2. Description of the Related Art
Sheet roofing products have been increasingly used in commercial building applications which involve large roof expanses, particularly with flat or shallow pitched roofs. This popularity of sheet roofing is due to a variety of factors, including convenience and speed of installation, reduced material and labor costs and longevity and reliability of the installed roof. Many sheet roofing products include synthetic rubber which are applied from rolls and attached to the roof via a variety of adhesives and fasteners.
While synthetic rubber sheets offer a number of advantages over competing products, including good weather resistance and elasticity, such rubber sheets, in and of themselves are not very resistant to puncture or stress cracking. Furthermore, rubber sheets, with their relatively smooth and moisture impervious surfaces, are resistant to bonding by most conventional adhesives, presenting a problem in reliably adhering the rubber sheets to the roof surface. Finally, where contiguous rolls of rubber sheets meet, they must overlap each other to form a weather impervious seal but these joints create a potential problem area where the overlapped rubber seams are adhered.
Previous attempts have been made to produce a composite roofing material including a synthetic rubber sheet with a fabric backing adhered thereto. One such roofing material is a membrane including a synthetic vulcanized rubber sheet having a thickness of from 40-70 mils backed by a polyester fleece-like matting having a thickness of about 40-80 mils which is produced by the Colonial Rubber Company of Dyersburg, Tenn. This product has proven to be very durable and crack and puncture resistant. In addition, the fleece-like matting provides an ideal bonding surface for roofing adhesives, such as the polyurethane foam adhesive taught in U.S. Pat. No. 4,996,812 (the '812 patent) to the present inventor, as well as asphalt and other adhesives.
Mass production of this composite material has proven to be problematical, however. In the known production method, the fleece-like matting is adhered to the rubber sheet during the vulcanization process, thus substantially complicating the vulcanization process and requiring very expensive, dedicated production machinery. At least partially as a result of the complexity of the process and equipment, material waste averages in excess of 30%. Since the membrane product is produced during the vulcanization process, the wasted material has virtually no other use. In addition, conventional vulcanization steam curing techniques cannot be used with the fleece lined material, thus requiring vulcanization time periods which are substantially increased over conventional vulcanized materials. Furthermore, it has proven impossible to produce a membrane with a selvedge on the underside of the membrane between the outside edge of the rubber sheet and the polyester matting. This is because, if such a selvedge is left, once the membrane is rolled into a roll for vulcanizing, the exposed selvedges will stick to adjacent layers in the roll, thus resulting in a congealed mass. Previous attempts to bond fleece matting to vulcanized rubber sheets have failed since no one has been able to reliably and effectively clean the talc or other non-stick coatings from the vulcanized rubber sheets. With the talc coatings intact on the rubber, conventional bonding agents will not work to bond the fleece matting to the rubber.
Furthermore, typical vulcanized rubber sheets are black in color, and with a fleece lining covering only the bottom surface of the rubber sheet, the exposed color of the roofing is black. However, many roofing applications, particularly in warmer climates, require white or light colored roofs for heat reflective properties, as well as aesthetics. While white colored rubber sheeting is available, it is considerably more costly than the typical black rubber. Furthermore, when exposed to weather and sunlight over a substantial period, white rubber is not very color stable.
It is clear then, that a need exists for an economical and reliable apparatus for producing a composite roofing material including a flexible vulcanized rubber sheet backed by a fleece-like matting. Such an apparatus should preferably use existing rolls of synthetic black vulcanized rubber (such as EPDM), which are available in commodity quantities, and should produce a roofing material which is durable and easy to apply to a roof surface. Such an apparatus must be capable of reliably and efficiently cleaning the talc or other non-stick coatings from the surfaces of the vulcanized EPDM rubber so that conventional bonding agents will adhere a fleece matting to the rubber. The roofing material thus produced should preferably include a selvedge on each side of the material underside between the edge of the rubber sheet and the matting for facilitating the attachment of sealing tape or adhesive between adjacent sheets as they are applied to a roof surface. Furthermore, the apparatus and method for producing the composite roofing material should preferably also be capable of producing a roofing material whose exposed upper side is white or otherwise lightly colored. Finally, the apparatus and method should be relatively economical to make and to run, and should be capable of efficiently producing large quantities of finished roofing material with minimal waste.